1. Field of the Invention
The invention relates to an apparatus for separation of a liquid from a multiphase fluid flow flowing through a pipeline, wherein the fluid flow is set in rotation so that it is separated into a central zone essentially containing gas, and an outer annular zone essentially containing liquid, and from which the gas and the liquid in the two zones are discharged via respective outlet means.
2. Description of the Prior Art
In offshore recovery of hydrocarbons (oil and gas), the produced fluids are often transported in relatively long pipelines and risers up from the seabed to the relevant production platform. The produced fluids usually consist of liquid (oil and water) in which gas and vapour are dissolved. In this connection different types of separation equipment are used for bulk separation of liquid from a flowing gas/vapour phase.
As mentioned in the introduction, it is known to separate a fluid flow into liquid and gas by the use of cyclone technique. The separation equipment used today is, however, relatively heavy and space-demanding, and is associated with relatively high building costs.
Thus it is an object of the invention to provide a separation apparatus of the relevant type wherein the apparatus has a compact construction at the same time as it is simple with respect to manufacture, installation and regulation.
For the achievement of the above-mentioned object there is provided an apparatus of the introductorily stated type which, according to the invention, is characterised in
that it comprises an essentially tubular casing arranged to constitute a part of the actual pipeline, a spin element for rotation of the fluid flow being located at the upstream end of the casing,
that the outlet means for the gas comprises an outlet element arranged at the downstream end of the casing and having a central, axially extending passage for the gas, and an outer surface which, together with the inner surface of the casing, forms an annulus for the inflow of liquid, a barrier for the liquid being formed at the downstream end of the element, and
that the outlet means for the liquid comprises an upwards open container arranged at the downstream end of the casing and adapted to receive liquid which flows into the annulus and partly runs down into the container from the bottom area of the casing at the container opening, and partly falls into the container from the area at said barrier.
With the present invention there is provided an apparatus making use of xe2x80x9cin-linexe2x80x9d technology to separate a fluid flow in a pipeline. The apparatus is based on the cyclone principle and is provided with an axial spin element simplifying the xe2x80x9cin-linexe2x80x9d method in that the supplied fluid flow and the separated gas fraction can flow in the pipeline axially into and out of the tubular casing. In this manner the casing can be simply installed in a straight pipeline stretch without any substantial modification of the existing pipe geometry.
The apparatus according to the invention can be used as an inlet arrangement to scrubbers and separators in order to improve the performance of such equipment. Further, the apparatus can be used as a stand-alone unit in pipes and pipelines in oil/gas wells, in pipelines on shore or on the seabed, or in processing plants on the shore or offshore.
In most cases the apparatus can be built with the same nominal diameter and specification as for the pipeline in which the separation is carried out. This will keep the costs down in application of the technology, and will considerably reduce the complexity of the relevant installations in relation to conventional separation technology. This will be the case with installations in new plants and pipelines, but the profit probably will be even larger when utilising the technology in existing plants and pipelines.
The advantages of an apparatus constructed in accordance with the invention can be summarised as follows:
1. Low weight in relation to conventional scrubbers and separators or slug catchers.
2. Low building costs in relation to the above-mentioned equipment.
3. The fact that one uses a pipeline as such for the separation apparatus, makes it possible to build the apparatus with very small dimensions.
4. The apparatus can be built according to the current pipe specification, so that protection equipment does not become necessary, as is the case for conventional pressure tanks in processing plants.
5. The actual separation of liquid from the gas/vapour phase takes place without the gas/vapour phase changing main direction. This results in that the pressure loss through the apparatus can be kept low at the same time as the separation of liquid takes place.
6. The apparatus can be installed horizontally as well as vertically with certain construction modifications.
7. The apparatus to a great extent is self-regulating, so that there is no need for complicated regulating means. Nevertheless, control of the apparatus with a regulating means may be appropriate in some applications.